Door mechanism



Jan. 16, 1934;

e. w. HEGEL DOOR MECHANISM Filed May 17, 19:50

IHVQHCOT George \N. .Hegel, 5 WM l-h's Attornes.

Patented Jan. 16, 1934 DOOR MECHANISM George W. Hegel, Schenectady, N.Y., assignor to General Electric Company, a corporation of New YorkApplication May 17, 1920. Serial No. 453,372

14 Claims.

My invention relates to door mechanisms, more particularly to doormechanisms for furnaces and the like, and has for its object theprovision of an improved mechanism of this character.

More specifically, my invention relates to door mechanisms for electricfurnaces wherein an opening is provided in the front or other suitablewall of the furnace in order to provide for communication with theheating chamber. It is the usual practice to provide furnaces of thischaracter with a door movable in a vertical direction from the closed tothe open position and vice versa. Some difficulty has been experiencedwith these furnaces because of the thermal losses oc-v curring at thedoor provided to close the furnace opening. Frequently these door losseswere sufficiently great to effect a reduction in the temperature at thefront of the furnace which, of course, r sulted in unequal temperatureconditions in J the heating chamber. In those furnaces wherein a work orloading shelf is provided before the furnace opening it has been verydiificult to thermally insulate the door, particularly at its lower end.Various arrangements have been used in Ian effort to overcome thisdifficulty. For in stance, a greater concentration of heat has beenprovided at the front portion of the heating chamber than in its rearportion so as to compensate for the thermal loss occurring at the door.in carrying my invention into effect in one form thereof, I provide thefurnace opening with a door having an area considerably greater than thearea of the opening so that when the door is closed a considerableoverlap is provided between the door and the furnace wall portionsurrounding the opening. This overlap serves to thermally seal thefurnace opening when the door is closed. I also provide means forsupporting the work or loading shelf so that it can be moved away fromits working position to permit the lower portion of the door to movebeyond the threshold of the furnace opening so that the door can belowered to its fully closed position and thereby establish the thermalseal about the opening.

I have further provided a simple and reliable operating means for thedoor. In carrying out this part of my invention, I provide the door withan operable connection between the door actuating means and the door sothat the door can be moved positively to its open position but isdisconnected from the actuating means in event of an obstruction to itsclosing movement.

For a more complete understanding of my invention reference should behad to the accompanying drawing in which Fig. 1 is a front elevae M tionof an electric furnace embodying my invention; Fig. 2 is a fragmentaryside elevation illustrating the furnace door in its closed position, andhaving parts in section so as to illustrate certain structural details;Fig. 3 is a View similar to Fig. 2 but illustrating the furnace door inits open position; and Fig. 4 illustrates in diagrams matic form asystem of control provided-for the door operating motor.

Referring to the drawing, I have shown my in-. vention in one form. asapplied to an electric furnace provided with a front opening therein,the door provided for this opening being mounted to move in a verticaldirection from the closed to the open position and vice versa. As shown,the electric furnace comprises a heating chamber 10 defined by suitableheat refractory walls, these wails, as shown, comprising an inner lining11 of a suitable heat refractory material, such as fire clay, and anouter lining 12 of brickwork formed from a suitable heat insulatingmaterial, such as diatomaceous earth. Preferably and as shown, an outermetallic casing 13 will be provided for the furnace walls. If desiredthe furnace walls may be supported upon a suitable structural framework14.

The front wall of the furnace is provided with an opening 15 whichserves to provide communication with the heating chamber 10, so thatwork may be placed in or taken out from the heating chamber, a suitableloading or Work shelf 16 being provided to facilitate the placing of thework in or theremoval of the work from the heating chamber. As shown, asuitable hearth plate 17 is mounted in the bottom of the heating chamberand is substantially flush with the threshold of the opening 15.

A suitable heat insulated door 20 is provided for the opening 15 and asshown is mounted be? fore the opening so that it is movable verticallyfrom its closed to its open position and vice versa. Preferably, thedoor will be provided with suitable vertically disposed metallic guides21 mounted on opposite sides of the furnace opening, the door beingprovided with suitable slides (not shown) which in the assembled furnaceare received by the guide members 21. These guides 21 are supported bysuitable column-like members 22 which preferably will be formed fromsome suitable metallic material such as steel. It will be understoodthat the guides 21 will be positioned with respect to the front wall ofthe furnace so that the door will be fitted closely to this wall.

In order to'thermally seal the front end of the furnace, the door isproportioned to have an area considerably larger than the front opening15 so that when it is in its closed position as shown in Figs. 1 and 2 aconsiderable overlap will be provided between the furnace wallssurrounding the opening 15 and the door. This overlap will besuiiiciently large to effectively insulate the entire front of thefurnace and thereby will considerably reduce the door losses. 1 havefound that this overlap provides for a substantial equalization oftemperature throughout the heating chamber. In order to more effectivelyseal the opening 15 when the door is in its closed position, I haveprovided auxiliary thermal seals 23 at the top and bottom edges of thedoor. As shown, each of these seals comprises a trough 24 in which sand25 or some similar material is placed, the top and bottom portions ofthe door being provided with suitable sealing members 26 which arereceived in the sand provided in the associated troughs when the door isin its closed position.

It will be observed that since the lower edge of the door projects aconsiderable distance beyond the level of the hearth when the door is inits closed position, suitable means must be provided for removing theshelf 16 from the path of the door in order to provide for its closingmovement. To this end, I have provided the shelf 16 with two portions,one a fixed portion 16a, which as shown is fixably secured to suitablesupporting brackets 2'7 disposed on opposite sides of the path ofmovement of the door so that it is substantially flush with the level ofthe hearth 17, and the other, a movable portion 16b. The shelf portion16a preferably will have a U-shape, the body of this portion beingspaced with respect to the front wall of the furnace, and its legs beingpositioned on opposite sides of the path of the door so that the bodytogether with its legs embrace the door when it is in its closedposition (see Figs. 1 and 2). This arrangement provides for a free andunobstructed movement of the door either to its open or to its closedposition. The other portion 16b of the shelf is mounted so that it canbe moved to a position substantially flush with the portion 16c and withthe hearth 17 and thereby establish an unbroken working surface for theshelf, or so that it may be moved to a position remote from its flushposition so as to permit the door to move to its cornpletely closedposition.

As shown, this shelf portion 16b is movably secured to the shelf portion16:! by means of supporting arms 160 which are welded or otherwisesuitably secured to the portion 16b and are pivotally connected to asuitable pin 28 that extends transversely of the portion 16a andthroughout substantially its length. The movable portion 16b is biasedto its flush position (Fig. 3) by means of a plurality of spring members39 each of which comprises a number of convolutions wrapped about thepin 28 and having projecting end portions 31 and 32, the portion 31being in engagement with a suitable stop member 33 provided on the fixedportion 16a of the shelf, while the other portion 32 engages the movableshelf portion 161). It will be observed by reason of this arrangementthat the forces exerted by the springs 30 always tend to move themovable shelf into its position flush with the portion 16a so as toestablish a complete working surface for the shelf. It will also beobserved that when the shelf portion 16b has been moved to its flushposition, the arms 16c engage the under surface of the fixed portion 16aso as to prevent further upward movement of the movable portion. While Ihave shown spring means so for biasing the movable shelf portion 16b toits flush position, it will be understood that any other suitablebiasing means, such as weights suitably connected with the movableportion, may be provided for this purpose. The stop member 33 which isof angular formation serves to strengthen the shelf portion 16a; asimilar member 33a extends transversely of the portion 16b so as toenhance its strength.

it will be observed that the resilient biasing means 30 provided for theshelf portion 162) permits this portion to be moved to its remoteposition by the downward movement of the door. Thus, as the door isbeing lowered to its closed position, its lower edge will engage themovable portion 16b of the shelf and move it to its remote position asshown in Fig. 2, the U-shaped fix-ed portion 15a receiving the door inits downward movement. It will also be observed that when the door isbeing raised to its open position the shelf will be establishedautomatically by means of the spring biasing means, the upward movementof the door, of course, permitting the shelf portion 16b to be moved toits flush position.

The movable shelf porti n 162') is positively locked in its shelfestablishing position by means of a pair of latch members 35 pivotallymounted opposite sides of the furnace opening. It will be observed thateach of these latch members is provided with a hoolr portion 36 at itslower end; and that this end is biased inwardly toward the furnaceopening by means of a tension spring 37 so as to cause the hook toengage the adjacent end edge of the movable shelf portion when it ismoved to its flush position by means of the springs 30. It will beunderstood that weights or other suitable means may be used to bias thelatches to their locking positions. Each latch member is also providedwith a cam--ike surface 38 which is engaged by the lower edge of thedoor in its downward movement so as to move the hook portions 36 out ofengagement with the movable shelf portion. Thus, the door in itsdownward movement automatically imlocks the movable shelf portion and alo moves it to its remote position so as to permit he door to move to itsfully closed position.

I provide suitable means for automatically operating the door to itsopen and closed positions. It will be observed that by reason of thecomparatively large area of the door, more specific-a1 ly because of itscomparatively long length, it is necessary that the door operatingmechanism have a rather high lifting range. In order to provide alifting mechanism which willmove the door completely to its openposition and which will not require a considerable amount of overhead aswould of the door operating mechanisms heretofore generally used, I haveplaced on opposite sides of the door a pair of vertically disposedoperating screws 40. It will be observed that these screws arepositioned in substantially parallel relation with each other and withthe line of movement of the door. The lower ends of these screws aresecured by suitable thrust bearings l2, while their upper ends .Lf

are secured against lateral movement by means of suitable bearings 4:3which are mechanically supported by means of the columns 22. Upon eachscrew 40 is threaded an operating member 14 shown as a nut. The door ismechanically connected to these nuts by means of a pair ,of brackets 45which are bolted or otherwise suitably secured to the door. It will beobserved that each bracket has a portion 45a projecting laterally fromthe door in a horizontal direction so as to rest upon the associatedoperating member or nut, and with a pair or" portions 45b projectinglaterally from the door in a vertical direction so as to receive theassociated nut between them and thereby prevent its rotation on itsoperating screw. It will also be observed that by reason of thisarrangement an upward movement of the nuts effected by the properrotation of the screw members Will cause the brackets 45, together withthe door which is secured thereto, to move in an upward direction, whileif the nuts be moved downwardly by the opposite rotation of the screwsthe door will be allowed to close under the influence of gravity.

This mechanical connection provided between the door and its operatingscrews is an important feature of my invention in that it provides for afreedom of movement of the operating mechanism from the door in adownward direction. Therefore, this mechanical connection serves as asafety feature; thus, if the door for any reason be blocked in itsdownward movement as by means of some material being left in the line ofmovement of the door, the operating mechanism would not jam since thedoor would be supported by the obstructing member, while the nuts wouldsimply move downwardly on the screws away from the door supportingbrackets. Moreover, this mechanical connection between the door and. thenuts 44 provides for irregularities in the movement of the door and alsofor its thermal expansion and contraction. This is effected by theprovision of suitable clearance between the brackets 45 and theoperating members 44. It will be understood that the door guides 21 willbe positioned relative to the door so as to permit a limited lateralmovement of the door, and thereby provide for its thermal expansion andcontraction.

The screws 46 are operated by means of a suitable electric motor 46which as shown is mounted beneath the furnace on the structuralsupporting Tame-work 14. This motor is mechanically coniected with eachof the screws 40 by means of a counter-shaft 47 positioned laterallybeneath the furnace and supported on the framework by means of suitablebearings 48. This countershaft is mechanically connected at its ends tothe screws 40 by means of suitable bevel gears 49. As shown, theelectric motor 46 is mechanically connected with the counter-shaft 4'7by means of a chain drive 50.

Preferably, although not necessarily so, the electric motor 46 will beof the alternating current type. In Fig. 4, I have showndiagrammatically a system of control whereby the motor 46 may beautomatically controlled by means of a simple push button station. Themotor 46 is electrically supplied by means of a suitable alternatingcurrent source 51 to which it may be connected by means of a pair ofcontrolling contactors 52 and 53, the contactor 52 being provided tocomplete an energizing circuit for the motor to close the door, whilethe contactor 53 serves to complete an energizing circuit for the motorto open the door. The energizing circuit for the contactor 52 iscontrolled by means of a closing push button 54, while the energizingcircuit for the contactor 53 is controlled by means of an opening pushbutton 55. The push button station further comprises a stop button 56.Suita able limit switches 57 and 58 are provided at the upper and lowerlimits of the doors motion so as to deenergize the motor when the doorhas been moved to its fully open or fully closed position. Although Ihave shown the limit switches to be operated by the nuts 44, it will beunderstood that they may be actuated by any suitable movable portion ofthe mechanism. Thus, for example, the door itself may be employed tooperate these switches. A suitable. overload relay 59 is provided forthe motor.

The operation of this portion of the mechanism is as follows: Assumethat the door has been moved to its fully open position (Fig. 3) so thatthe upper limit switch 57 has been moved to its open position (Fig. 4)to deenergize the operating motor; and further that it be desired toclose the door. In order to cause the door to move to its closedposition it is merely necessary to momentarily depress the closing pushbutton 54. It will be observed that when this push button is depressedso as to close its lower set of contacts an energizing circuit for theclosing contactor 52 will be completed from the upper conductor of thealternating current supply source 51 through the conductor 60, theconductor 61, the stop push button'56, the conductor 62, the lower limitswitch 58 which will have been allowed to close when the door was beingmoved to its open position, the conductor 63, the closed upper contactsof the opening push button 55, the closed lower contacts of the pushbutton 54, which will be in its depressed position, the conductor 64,the operating coil of the closing contactor 52, the conductor 65, theoverload relay 59, the conductor 66 and thence through the conductor 67to the middle conductor of the alternating current supply source 51. Theclosing contactor 52 closes in response to the completion of thiscircuit and in closing establishes a holdlimit switch 58 to open andthereby deenergize the motor.

In order to open the door it is merely necessary to depress the openingpush button so as to close its lower set of contacts. When this buttonis depressed an energizing circuit for the opening contactor 53 will becompleted from the upl per conductor of the alternating current supplysource through the conductor 60, the conductor 61, the stop push button56, the conductor 62, the closed upper limit switch 57, the closing pushbutton 54, the lower contacts of the push button V 55 which Will havebeen bridged by the depression of this button, the conductor '70, theconductor '71, the operating coil for the opening contactor 53, theconductor 72, the conductor 65, the

overload relay 59, the conductor 66 and thence through the conductor 6'7to the middle conductor of the alternating current supply source. Thecontactor 53 in closingestablishes a power circuit for the motor 46 tooperate the door in an open direction, and also establishes a holdingcircuit for its operating coil by means of an interlock 73. The doorupon being moved to its completely open position will open the upperlimit switch 57 to deenergize the motor.

It will be understood that after the motor has been enerl gized to movethe door either to its open or to its closed position it may bedenergized by means of the stop button 56 so as to stop the door at anydesired position within the limits 'ofits movement.

I have provided suitable means for releasing the operating members ornuts or in the event the limit switches provided for deenergizing themotor fail for any reason. It will be observed that the upper and lowerportions e2a, 42b of the screws 40 are not threaded and are reduced indiameter so that if the nuts 44 be moved in either direction beyond thethreaded portions of their screws, they will be received by the reducedportions, after which it will be impossible for the screws to impart anyfurther motion to the nuts, and consequently to the door. In otherwords, these screws will have been rendered ineffective to impart anyfurther motion to the door until the nuts have been rethreaded. Thesereduced portions are positioned with respect'to the limit switches sothat normally the nuts will not ride off of the threaded portions of thescrews, the motor being deenergized by the proper operation of the limitswitches before such an operation can take place.

It will be understood that when the 'door has been moved to itscompletely closed position and the lower limit switch 58 has been openedso as to deenergize the motor it is possible that the motor I anddriving mechanism will continue to rotate by reason of the inertia oftheir parts so as to carry the operating members or nuts 44 beyond'theirlower limiting positions. It is possible that the driving mechanism attimes will possess sufficient inertia to cause the nuts to ride offtheir threaded screw portions. In order to prevent this condition, Ihave provided suitable means for damping the door operating mechanismafter the door has been moved to its fully closed position and the motorhas been deenergized. To this end, I have provided suitable compressionsprings "'74 surrounding the reduced portions 4239 provided on the lowerends of the screws 10, and supported on the screws by m ans of suitablecollars 5. It will be observed that these springs are such a length thatthey will extend substantially throughout the full lenght of theselowered reduced sections, whereby in the event the operating mechanismcontinues to move by reason of its inertia, the nuts or operatingmembers i l will engage the upper ends of the compression springs which,of course, will then operate to retard further downward movement of thenuts. The springs in effect impose a load on the operating mechanismwhich will quickly brin the mechanism to rest, it being understood thatthe springs will have suflicient strength to bring the mechanism to restbefore the nuts have'moved a sufficient distance to ride oil thethreaded sections of the operating screws.

It will be understood that any suitable heating means may be providedfor the heating chamber. I prefer, however, to use electrical heatingelements which may be mounted alo of the heating chamber and also or Asshown, suitable resistors 76 are mounted along the sides of the chamber1%), these resistors being sus-- pended from suitable hooks 77 attachedin any well-known manner to the furnace walls 11. Refractory spacingmembers '78 are also mounted on the furnace walls and are arranged tohold the convolutions of the resistors in the proper spaced relation.Mounted in the bottom of the heating chamber under the hearth plate 17are other resistors 80 preferably formed into a plurality of parallellengths (not shown). Each heating resistor 80 is supported upon asuitably refractory spacing member 81 which rests on the floor of theheating chamber and which is provided with suitable recesses 82 in whichthe convolutions of the resistors are kept in proper spaced relation. Itwill be understood that both the resistors '76 and 80 willbe formed fromany suitable heat resisting material such as nickel chromium alloy. Itwill also be understood that suitable connections will be made to theseresistors in any well-known manner with a suitable source of electricalsupply.

While I have shown a particular embodiment of rnyinvention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made, and I, therefore, contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

- 1. Door mechanism for furnaces and the like provided with wallsforming a heating chamber having an opening therein that is providedwith a threshold, comprising a door for c. sing said opening having anarea substantially larger than the area of said opening so as to providean overlap between said door and the wall portion below said threshold,a shelf, means movably supoorting said shelf so that it can be moved toa doe.- ing position before said opening substantially flush with saidthreshold or be removed from said opening to permit said door to closeand means operably associated with said shelf for moving it to itsworking position substantially flush with said threshold when said dooris moved to any open position within its range of movement to provideaccess to said heating champer.

2. Door mechanism for furnaces and the like provided with walls forminga heating chamber having a side door opening therein, comprising a doorfor said opening mounted for movement in a vertical direction from theclosed to the open position and vice versa and proportioned to provide aconsiderable overlap between the wall portion surrounding said openingand said door when the latter is in its closed position so as tothermally seal said opening, a shelf, means movably mounting said shelfso that it can be moved to a rking position before said openingsubstantially hush with the threshold of opening and to a positionremote from said working position and sh with said threshold so that saison is moved to its working position when said door is moved verticallyto any open position within its range of movement to provide access tosaid heating chamber.

3. Door mechanism for furnaces and the like provided with walls forminga chamber having an opening therein, comprising a door for said openingproportioned so that when it is in its position to close said opening,at least one edge of said door projects beyond the associated edge ofsaid opening, a shelf movably supported so that it can be moved to aposition substantial? flush with said associated edge and so that it canbe moved to a. point remote therefrom to provide for the closing of saiddoor, and spring means engaging said shelf so as to move itautomatically to its flush position when said door is moved to its openposition.

4. Door mechanism for furnaces and the like eans biasing said shelf toits workprovided with walls forming a heating chamber having a sideopening therein, comprising a door for said opening mounted for verticalmovement before said opening so that it can be raised to an openposition and can be lowered to its closed position and proportioned toprovide a considerable overlap between the wall portion surrounding saidopening and said door when the latter is in its closed position so as tothermally seal said opening, a shelf movably mounted so that it can bemoved to a working position before said opening and to a position remotefrom said working position, and resilient means biasing said shelf toits working position so that as said door is raised to its openposition, said shelf is moved concurrently to its working position bysaid resilient means, said shelf being moved to its remote positionagainst the bias of said resilient means by said door as it is beingclosed.

5. Door mechanism for furnaces and the like provided with walls forminga heating chamber having a side opening therein, comprising a doormounted for vertical movement before said opening so that it may bemoved away from said opening to provide for communication therethroughand having a portion projecting beyond the hearth level of said opening,a shelf before said opening provided with a portion substantially flushwith the hearth level of said opening and a portion pivotally secured tosaid first portion so that it can be moved to a position substantiallyflush with said first portion or to a position remote therefrom, meansfor moving said second portion to its flush position as said door isbeing moved to its open position, said means providing for the movementof said shelf to its remote position when said door is closed and meansdependent upon the position of said door for looking said movableportion in its flush position before said opening.

6. Door mechanism for furnaces and the like provided with walls forminga heating chamber having a side opening therein, comprising a door forsaid opening mounted for vertical movement before said opening so thatit can be raised to an open position and can be lowered to its closedposition and proportioned to provide a considerable overlap between thewall portion surrounding said opening and said door when the latter isin its closed position so as to thermally seal said opening, a shelfbefore said opening comprising a fixed portion mounted on substantiallythe same level as the hearth of said furnace and in spaced relation withsaid opening so that said door can be moved between said portion andsaid opening, and a second portion movably mounted so that it can bemoved to a position between said fixed portion and said opening toprovide a substantially unbroken shelf working surface between saidfixed portion and said opening and so that it can be moved to a positionremote from said opening, means biasing said movable portion, so that assaid door is raised to its open position, said shelf is automaticallyestablished, said biasing means providing for the movement of saidmovable portion to its remote position so as to permit said door toclose, and means for locking said movable member in its shelfestablishing position comprising means engaged by said door as it isbeing moved to its closed position arranged to render said locking meansineffective.

7. Door mechanism for furnaces and the like provided with walls forminga heating chamber having a front opening therein, comprising a doorbefore said opening mounted for vertical movement so that it can bemoved to a position remote from said opening to provide forcommunication therethrough and can be returned to close said opening,said door being proportioned to provide a substantial thermal overlapbetween the furnace wall portion surrounding said opening and said doorwhen said door is in its closed position, a work shelf before saidopening comprising a stationary portion substantially flush with thehearth level of said furnace and spaced from said opening so as topermit said door to move to it closed position and a second portionpivotally secured to said first portion so that it can be moved to aposition substantially flush with said first portion and with saidhearth level or can be moved away from said flush position to providefor the closing movement of said door, resilient means operablyassociated with said pivoted portion so as to bias it to its flushposition but providing for movement of said portion to its remoteposition by said door as said door is moved to its closed position, anda latch member biased to engage said pivoted portion when it is in itsflush position so as to lock said portion in said flush position, saidlatch member being moved to disengage said pivoted shelf portion by saiddoor as the latter is being moved to its closed position.

8. Door mechanism for furnaces and the like provided with walls forminga heating chamber having a side opening therein comprising a door forsaid opening mounted for movement in a vertical direction from theclosed to the open position and vice versa and when closed having itslower end portion projecting beyond the hearth level of said opening, ashelf, means pivotally supporting said shelf so that it can be movedinto the line of motion of said door to a working position in front ofsaid opening and to a position remote from said working position so asto permit said door to be moved to its closed position, said doorengaging said shelf when being moved to its closed position so as tomove said shelf to its remote position, actuating means for said doorand an operable connection between said actuating means and said door sothat the door is moved positively to its open position, but is releasedfrom said actuating means in the event the motion of the door is impededunduly by said shelf or by an obstacle on said shelf and in the dooropening.

9. Door mechanism for furnaces and the like having an opening thereincomprising a door for said opening, a shelf pivotally mounted beforesaid opening so that it can be moved into the line of movement of saiddoor to a position substantially flush with the threshold of saidopening and to a position remote therefrom, said shelf being engaged bysaid door and moved to said remote position when said door is closed andmeans arranged to move said shelf to said flush position when said dooris moved to any open position within its range of movement to provideaccess to said furnace.

10. Door mechanism for furnaces and the like having an opening thereincomprising a door for said opening, a shelf, means mounting said shelffor movement between a working position substantially flush with thethreshold of said opening and a position remote therefrom and resilientmeans biasing said door to said flush position, the shelf being movedfrom said flush position against the bias of said resilient means bysaid door as the door is being closed.

11. Door mechanism for furnaces and the like having an opening thereincomprising a door for said opening, a shelf, means mounting said shelffor movement between a working position substantially flush with thethreshold of said opening and a position remote therefrom and a latchmember arranged to engage said shelf to lock it in said flush positionand to be operated by said door when said door is being closed so as torelease said shelf.

12. Door mechanism for furnaces and the like having an opening thereincomprising a door for said opening, a shelf, means mounting said shelffor movement between a working position substantially flush with thethreshold of said opening and a position remote therefrom, spring meansarranged to move said shelf to said flush position and providing for themovement of said shelf from said flush position to said remote positionand locking means arranged to hold said shelf in said flush position andprovided with a member arranged to be engaged by said door as it isbeing closed so as to release said locking means.

13. Door mechanism for furnaces and the like having an opening thereincomprising a door for said opening, a shelf, means before said openingpivotally mounting said shelf for movement into the line of movement ofsaid door to a position substantially flush with the threshold of saidopening and to a position remote therefrom, spring means engaging saidshelf and biasing it to said flush position, and latching means forholding said shelf in said flush position, said latching means beingengaged by said door when the latter is being moved to its closedposition so as to release said shelf, the shelf being engaged by saiddoor when it is thus moved to its closed position so as to be moved fromsaid flush to said remote position.

14. Door mechanism for furnaces and the like having an opening thereincomprising a door for said opening, a shelf, means movably supportingsaid shelf in a position in the line of movement of said door so thatsaid shelf is engaged by said door and moved away from said positionwhen the 1 door is closed and spring means engaging said shelf to returnit to said position when said door is opened.

GEORGE W. HEGEL.

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